Solar cells having a transparent composition-graded buffer layer

Abstract

A solar cell includes a first layer having a first-layer lattice parameter, a second layer having a second-layer lattice parameter different from the first-layer lattice parameter, wherein the second layer includes a photoactive second-layer material; and a third layer having a third-layer lattice parameter different from the second-layer lattice parameter, wherein the third layer includes a photoactive third-layer material. A transparent buffer layer extends between and contacts the second layer and the third layer and has a buffer-layer lattice parameter that varies with increasing distance from the second layer toward the third layer, so as to lattice match to the second layer and to the third layer. There may be additional subcell layers and buffer layers in the solar cell.

Description

[0001] This invention was made with Government support under Contract No. F29601-98-2-0207 awarded by the United States Air Force. The Government has certain rights in this invention.

[0002] The present invention generally relates to semiconductor materials and, more specifically, to solar cells. BACKGROUND OF THE INVENTION

[0003] A solar cell is a photovoltaic (PV) device having one or more photovoltaic junctions. Each junction is formed by a photovoltaic semiconductor layer. At each junction, incident light energy, and specifically solar energy, is converted to electrical energy through the photovoltaic effect.

[0004] The interest in solar cells has been increasing due to concerns regarding pollution and limited available resources. This interest has been for both terrestrial and non-terrestrial applications. In space applications, the use of nuclear or battery power greatly increases a spacecraft's payload for a given amount of required power to operate the satellite. Increasing t...

Examples

Embodiment Construction

[0039]FIGS. 1-10 depict multijunction solar cells that incorporate the present approach. In each of these multijunction solar cells, sunlight from the sun is incident in a direction 18, and there are electrodes (not shown) to conduct the electrical current generated by the solar cell. When used to compare two layers, “upper” or “above” or “overlying” refers to a layer closer to the sun, and “lower” or “below” or “underlying” refers to a layer further from the sun or other source of illumination.

[0040]FIG. 1 depicts a first embodiment of a multijunction solar cell 20. The multifunction solar cell 20 includes a first layer 22 having a first-layer-lattice parameter. The first layer 22 may be an inert substrate, or it may be a photoactive layer made of a photoactive first-layer material. The multijunction solar cell 20 further includes a second layer 24 having a second-layer lattice parameter different from the first-layer lattice parameter. The second layer 24 includes a photoactive s...

[0001] This invention was made with Government support under Contract No. F29601-98-2-0207 awarded by the United States Air Force. The Government has certain rights in this invention.

[0002] The present invention generally relates to semiconductor materials and, more specifically, to solar cells. BACKGROUND OF THE INVENTION

[0003] A solar cell is a photovoltaic (PV) device having one or more photovoltaic junctions. Each junction is formed by a photovoltaic semiconductor layer. At each junction, incident light energy, and specifically solar energy, is converted to electrical energy through the photovoltaic effect.

[0004] The interest in solar cells has been increasing due to concerns regarding pollution and limited available resources. This interest has been for both terrestrial and non-terrestrial applications. In space applications, the use of nuclear or battery power greatly increases a spacecraft's payload for a given amount of required power to operate the satellite. Increasing t...

Examples

Embodiment Construction

[0039]FIGS. 1-10 depict multijunction solar cells that incorporate the present approach. In each of these multijunction solar cells, sunlight from the sun is incident in a direction 18, and there are electrodes (not shown) to conduct the electrical current generated by the solar cell. When used to compare two layers, “upper” or “above” or “overlying” refers to a layer closer to the sun, and “lower” or “below” or “underlying” refers to a layer further from the sun or other source of illumination.

[0040]FIG. 1 depicts a first embodiment of a multijunction solar cell 20. The multifunction solar cell 20 includes a first layer 22 having a first-layer-lattice parameter. The first layer 22 may be an inert substrate, or it may be a photoactive layer made of a photoactive first-layer material. The multijunction solar cell 20 further includes a second layer 24 having a second-layer lattice parameter different from the first-layer lattice parameter. The second layer 24 includes a photoactive s...

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